The technique of step acousto-optical deflection and its application in high speed interferometric photography

This paper presents the technique of step acousto-optical deflection and its application in high speed interferometric photography. When a light beam carrying the interferogram information passes through an acousto-optical deflector, it is deflected into 10 patterns (φ6 mm-φ8 mm in diameter) in time-sequence and recorded on a fixed film under the action of step pulsed ultrasonic waves. The exposure time of every pattern is adjustable within the range of 10^(-5)-3 ×10^(-6) s and the interval between two patterns is 10^(-5) s. The multi-frame interferograms of the transient combustion field of the first fire composition ignited by laser are recorded by using this method with combination of a laser interferometer, and the temperature distribution and its change with time is calculated quantitatively.

Simulation and Experimental Study of Dynamic Characteristics of a Pneumatic Actuator in Air Splicer

Splicing process parameters determined by dynamic characteristic of pneumatic actuator in air splicer have a significant influence on the performance of spliced yarn. Both gas thermodynamic and pneumatic actuator dynamic models, which were solved by the Runge-Kutta algorithm, were established to analyze the relationship among structural parameters of a pneumatic actuator and splicing process parameters such as splicing duration and gas consumption. Additionally,a visualization test bench to observe the dynamics of the pneumatic actuator and a mass flow measurement system to track splicing duration and gas consumption were designed. Comparisons between experimental data and simulation results show that the mathematical model accurately accounts for the dynamic characteristics of the pneumatic actuator,and consequently predicts splicing process parameters, which provides a theoretical foundation for the design optimization of air splicer.

Laser induced self-propagating high-temperature synthesis of TiNi alloy

TiNi alloy, especially porous TiNi, a good biocompatible material, can be made by laser induced self-propagating high-temperature synthesis (SHS). A 40-W CO2 laser was used to ignite the powders of Ti and Ni, and TiNi intermetallic compound was synthesized by SHS in a reaction kettle of stainless steel. High-speed photography, X-ray diffraction, and scanning electron microscopy were used to investigate and analyze the reaction process, phase composing, and microstructure of the product, respectively. The influence factors on the reaction process and the product were discussed. The results indicate that laser induced SHS is an efficient, energy-saving method; The phase ingredient of the product consists of TiNi, Ti2Ni, and Ni3Ti. With the increase of the preparing pressure of the sample, the reacting rate decreases; With the increase of the laser power and the preheating temperature, the reacting rate increases. Under the condition of 30℃/min, the synthesis reaction had been carried out consistently and completely.

Calculation and verification of formula for the range of sprinklers based on jet breakup length

Jet breakup length is an important parameter which reflects the length of sprinkler range.Based on the linear instability theory,the dispersion equation of cylindrical jet was established and the theoretical value of jet breakup length was calculated.The jet breakup length and initial amplitude of surface wave were measured by applying the high-speed photography technology.Meanwhile,the numerical simulation was conducted by combining Level Set-VOF method for describing the jet breakup length to verify the theoretical and experimental results.Within the jet velocity and working pressure range of discussion,the results of comparison showed that the theoretical analysis gave a reasonable explanation to the influence of jet velocity,nozzle diameter and nozzle cone angle on jet breakup length.Comparing the theoretical value of jet breakup length with the experimental and simulated values,the three results accorded one another.The experimental jet breakup lengths were the lowest and the simulation values were the largest,and the relative error was less than 10%,especially the theoretical value was closer to the average value.For choosing the theoretical calculation of jet breakup length,a semi-empirical and semi-theoretical formula of range for the rotating sprinkler was concluded by the curve fitting method and the fitting formula was verified.The results showed the high accuracy of the ranges determined by this formula and the average relative error was less than 2.5%.The new formula was in good agreement with the data of different types of sprinklers comparing with other empirical formulas,and the error was only 5%.Meanwhile,the possibility of using this formula widely to determine the ranges of same series of sprinkler was confirmed.

Experimental Investigation of the Dynamic Deformation of LY12 Aluminum Plate Heated by Strong Electrical Current

The moire interferometry method was used with holographic gratings for high temperature and high speed photography to measure the dynamic deformation of LY12 aluminum plate with a central hole under tensile loading condition and heated by a strong current. Transient fullfield fringe patterns were acquired during the heating process. Transient temperature of the specimen was simultaneously recorded by a temperature measurement system. The experimental results show that dynamic moire fringe patterns can be measured during high heating rate conditions using high speed photography.